Back cushion



FIG. 1 is a front perspective view of a back cushion;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a left side view thereof;

FIG. 7 is a top view thereof; and,

FIG. 8 is a bottom view thereof.

The broken lines show portions of the design that form no part of the claim. 

CLAIM The ornamental design for a back cushion, as shown. 